As the dimensions of semiconductor devices and components continue to decrease, the demand for enhanced semiconductor wafer inspection capabilities will continue to increase. One manner in which semiconductor wafer inspection procedures may be improved is through the reduction of dynamic range during semiconductor wafer imagery acquisition. The reduction of dynamic range in inspection imagery data allows for improved defect detection sensitivity during wafer inspection process. In addition, the reduction of dynamic range in inspection imagery data may aid in eliminating common side effects attributed to high dynamic range semiconductor wafer inspection. The side effects include ghosting, flaring, or ringing produced in the imaging optics of an inspection system.
Traditional methods of dynamic range reduction include the saturation of portions of an image obtained from a semiconductor device in order to acquire adequate sensitivity in the darker (array) portions of the substrate. This method does not allow for optimum inspection sensitivity in saturated areas of the wafer. In order to partially compensate for this shortfall, systems and users commonly perform two or more passes, at different illumination levels, over the wafer.
Another commonly utilized methodology includes the reduction in global illumination such that the entirety of a given wafer is illuminated at levels below the various saturation levels, but also below an optimal illumination level for any given device features. In addition, in settings where the illumination of a given illumination source is optimized for darker regions of a wafer pattern, the inspection sensitivity in these dark regions becomes compromised due to the high levels of unwanted light from brighter regions.
The deficiencies described above reduce wafer fabrication throughput and cost of ownership. It would therefore be desirable to provide a system and method, which cures the deficiencies of the prior art.